DE102018109067A1 - A method of gear grinding a gear workpiece and a grinding machine with a control for generating grinding of a gear workpiece - Google Patents

Abstract

A method of gear grinding a gear workpiece (W1) with a dressable grinding worm (2), wherein during grinding, the grinding worm (2) rotates about a tool rotation axis (B) and the gear workpiece (W1) rotates about a workpiece rotation axis (C) and relative movements are performed between the grinding worm (2) and the gear workpiece (W1), and after performing a dressing operation of the grinding worm (2) performed by a rotary drivable dresser (4), the following steps are performed: - Performing a relative shift movement between the grinding worm (2) and the gear workpiece (W1) parallel to the tool rotation axis (B), - performing an axially parallel relative movement between the grinding worm (2) and the gear workpiece (W1) parallel or oblique to the Workpiece rotation axis (C), wherein a ratio between the shift movement and the axis-parallel Rela is predetermined, which is changeable.

Description

Field of the invention

The invention relates to a method for generating grinding of a gear workpiece. In particular, it concerns a device and a method for generating grinding of a gear workpiece with a multi-dressable grinding worm. It also concerns a grinding machine with a control for generating grinding of a gear workpiece.

Background of the Invention, Prior Art

In 1 are the elements of an exemplary grinder 100 shown, wherein in this illustration, only the essential elements are labeled, and that these are the tool spindle 1 including a grinding tool 2 and a workpiece spindle 3 with a workpiece W1 , In addition, in this illustration, some of the axes are shown for the Wälzschleifen of the workpiece W1 can be used. These are three linear axes X . Y and Z , There is also a rotation axis B to the grinding tool 2 to be able to drive. The tool spindle 1 including the grinding tool 2 can be about a pivot axis A be pivoted to the slope of the grinding worm 2 with the helix angle of the workpiece W1 to get in line. Furthermore, there is a rotation axis C (also called workpiece axis) to the workpiece W1 to be able to drive. Based on 1 It can be seen that a whole series of coordinated linear, rotary and pivotal movements are required to a workpiece W1 with a grinding tool 2 to be able to grind.

One of the factors that influences the economy of such a grinding machine 100 has, is the life of the grinding tool 2 (here in the form of a grinding worm). The faster the tool 2 worn, the fewer workpieces W1 can with a tool 2 to be edited. There are therefore different strategies to a grinding worm 2 use as economically as possible.

Among other things, it works with different shift strategies. The continuous shift (sometimes referred to as diagonal shifting) is a process in which the grinding machine 100 performs a continuous shift movement parallel to the Z-axis, around the grinding worm 2 relative to the workpiece W1 to move. This form of shifter ensures that areas with new or sufficiently abrasive grains of the grinding worm 2 be used. By shifting, not only is the geometric accuracy of the gear workpieces W1 ensured, but it can be largely prevented thermal damage to the tooth flanks.

There are also non-continuous shift strategies that are based, for example, on the grinding worm 2 in different areas for roughing and finishing a workpiece W1 is divided.

There are also shift strategies in which a shifter each after machining a workpiece W1 takes place, for example, to process the next workpiece another area of the grinding worm 2 to be able to use.

In addition, a Schleifhub is required, which is required to workpieces W1 to be able to grind b2 over its entire tooth width. The grinding stroke comprises in a straight-toothed spur gear W1 , as in 1 shown a linear movement of the grinding worm 2 parallel to the X-axis of the machine 100 ,

The shift strategies for continuous shifting are typically defined in the prior art by a ratio of the shift travel to the stroke. That is, in conventional generating grinding, the amount of continuous displacement of the grinding worm becomes 2 determined by the constant ratio Shiftweg to stroke, this determination can be made hubspezifisch. In these shift strategies, the shiftweg is a length along the screw axis (referred to here as the B axis), ie along the screw width b0 and the stroke is a length along the workpiece axis (here referred to as C-axis).

Furthermore, a feed movement is performed to a tooth of the grinding worm 2 to a final depth in a tooth gap of the gear workpiece W1 to let in. The delivery movement takes place in the example of 1 parallel to the Y axis of the machine 100 ,

There is a need to further optimize generating grinding with a grinding worm.

The object of the present invention is therefore to develop a control or software for a grinding machine for the gear grinding of gears, which has a reproducibly high precision of the grinding processing and nevertheless a high efficiency. In addition, a suitable method is to be provided that helps to improve the efficiency.

In particular, it is a question of providing a grinding machine for the generating grinding of spur gears, which allows a consistently high degree of precision of the grinding of a series of workpieces.

A corresponding method of the invention is characterized by the features of patent claim 1. A corresponding grinding machine of the invention is characterized by the features of claim 11.

• - Shiften der Schleifschnecke relativ zum Zahnrad-Werkstück parallel zu der Werkzeugrotationsachse,
• - achsparalleles Relativbewegen parallel oder schräg zu der Werkstückrotationsachse, die vorzugsweise senkrecht oder schräg zur Werkzeugrotationsachse steht,

wobei ein Verhältnis zwischen dem Shiften und dem achsparallelen Relativbewegen vorgegeben ist, das veränderlich ist, so dass beim Wälzschleifen eines Zahnrad-Werkstücks nach dem Abrichtvorgang ein anderes Verhältnis zum Einsatz kommt als beim Wälzschleifen eines Zahnrad-Werkstücks vor dem Abrichtvorgang.The method of gear grinding a gear workpiece employs a dressable grinding worm that is rotationally driven about a tool rotation axis while the gear workpiece is being rotated about a workpiece rotation axis. In addition, during grinding, the grinding worm carries out hobbing movements relative to the gear workpiece. The grinding worm is subjected to a dressing process from time to time or as required. After the dressing process, which serves to dress the grinding worm, the following movements are carried out for generating a gear workpiece:

• Shifting the grinding worm relative to the gear workpiece parallel to the tool rotation axis,
• axis-parallel relative movement parallel or oblique to the workpiece rotation axis, which is preferably perpendicular or oblique to the tool rotation axis,

wherein a relationship between the shift and the axis-parallel relative movement is predetermined, which is variable, so that when Wälzschleifen a gear workpiece after the dressing process, a different relationship is used to when Wälzschleifen a gear workpiece before the dressing process.

Altering the ratio may be done prior to dressing, during dressing or after dressing so that it becomes effective in the hobbing of the subsequent gear workpiece.

In at least a part of the embodiments, the hobbing is performed at a constant ratio.

In at least part of the embodiments, the word "variable" is used to indicate that said ratio is not constant.

In at least part of the embodiments, the word "variable" is used to specify that said ratio is adjusted step-by-step, preferably after each dressing of the grinding worm, respectively.

At least a portion of the embodiments involve a particular form of shifter that is performed during gear grinding of a plurality of gear workpieces after performing a dressing operation.

In at least some of the embodiments, a dressable grinding worm is used, which can be dressed several times, whereby the diameter of the grinding worm is reduced by the dressing, and wherein the relationship between the shifting and the axis-parallel relative movement is changed with the decreasing diameter of the grinding worm , That is, it is not worked in these embodiments with a fixed ratio of Shiftweg to Hubweg, but this ratio is adjusted specifically step-by-step. The term "stroke" is used here partly because it has prevailed in the literature. This refers to a relative movement between grinding worm and gear workpiece, which is parallel to the axis or oblique to the workpiece rotation axis. This axis-parallel relative movement may be e.g. by driving a single linear axis (sometimes also called stroke axis) or by superimposing several movements in a machine are generated.

In at least a portion of the embodiments, varying the ratio between the shift and the axis-parallel relative movement is performed parallel or obliquely to the workpiece rotation axis based on an engagement density, wherein the engagement density is a tool-specific size. This Altering the ratio is not carried out continuously during the hobbing but discontinuously (in the sense of stepwise), for example after each dressing or after a number of dressing operations.

In at least a part of the embodiments, changing the ratio between the shift and the axis-parallel relative movement is made parallel or oblique to the workpiece rotation axis based on an engagement density defined as a tool-specific size, thereby changing the ratio between the shift and the axis-parallel relative movement in that the engagement density can be kept constant or approximately constant during the actual gear grinding of the gear workpiece.

In at least a part of the embodiments, a grinding machine is used which comprises at least one spindle for picking up and rotationally driving a grinding worm, a spindle for picking up and rotationally driving a gear workpiece, and a plurality of NC controlled axes adapted for the purpose of hobbing relative movements the grinding worm perform relative to the gear workpiece. Furthermore, the grinding machine comprises a dressing device and a controller, which is connectable to the grinding machine, that a process after a dressing process is performed, which comprises a relative, axially parallel relative movement between the grinding worm and gear workpiece, which is parallel to the axis or obliquely to the workpiece rotation axis, and comprising a relative shift movement between grinding worm and gear workpiece, wherein a ratio between the shift movement and the axis-parallel relative movement is predetermined, which is variable.

In at least part of the embodiments, the controller is designed or programmable to be able to perform the steps of the method of the invention after each dressing operation or after two or more than two dressing operations.

The invention can be applied especially to straight-toothed spur gears and helical spur gears. The invention leaves e.g. on Beveloide (i.e., on gears with conical teeth).

In at least some of the embodiments, preference is given to the circumstances or technological possibilities which have proven to be reliable even at the smallest diameter of the multiple-dressing grinding worm. That one can e.g. assume a tool-specific output that has proven itself in practice. This size of performance is a measure of the grinding ability of the grinding worm, if it has reached its minimum valid diameter due to multiple truing. As it is known from experience that the grinding worm still achieves a good and reliable grinding performance when it reaches its minimum valid diameter, an extrapolation for a modified shift strategy can be made on the basis of this known grinding performance.

The invention uses in at least part of the embodiments a measure of the grinding ability of the grinding worm to use this measure to adjust the ratio between a relative shift movement and the lifting movement (i.e., a relative axis-parallel movement parallel or oblique to the workpiece rotation axis).

In at least a part of the embodiments, a ratio between the shift and the axis-parallel relative movement is predetermined parallel or obliquely to the workpiece rotation axis, which is variable.

In order to make this variability technologically useful, a process variable can be defined, which is referred to here as an example of intervention density. In the corresponding embodiments, the shift strategy is adjusted as a function of the intervention density.

In at least a part of the embodiments, an intervention density is used as a measure of an upper limit which has proven itself when using a grinding worm with its minimum valid diameter. Through technical measures, when using the grinding worm, it is ensured that in no other area of the grinding worm can an effective engagement density occur which is greater than the upper limit value.

In at least a portion of the embodiments, the grinding machine includes a computer, or an interface for connection to an (external) computer, the computer being configured to specify the relationship between the shift movement and the axis-parallel relative movement.

In at least a portion of the embodiments, the grinding machine comprises a computer, or an interface for connection to an (external), the computer is configured to allow in a preparatory step to determine the course of contact lines on tooth flanks of the grinding worm, said In the case of gear grinding, contact lines between the gear workpiece and the grinding worm result in contact lines, and a mutual distance between at least two adjacent contact lines can be determined in order to allow calculation of an engagement density as a number of contact points per unit length.

In at least part of the embodiments, an external computer, e.g. can be connected to an interface of the grinding machine via an internal or external network, used e.g. specify the relationship between the shift movement and the axis-parallel relative movement and / or to pass by means of software or a software module corresponding specifications for changing the ratio to the grinding machine.

Further preferred embodiments can be found in the respective subclaims.

list of figures

• 1 zeigt eine schematische Perspektivansicht einer Schleifmaschine, die dazu ausgelegt ist mit einem Schleifwerkzeug ein Werkstück schleifend zu bearbeiten;
• 2A zeigt eine schematische Seitenansicht eines beispielhaften, geradverzahnten Stirnrads, wobei anhand dieser Ansicht Grundbegriffe definiert werden;
• 2B zeigt eine schematische Projektion einer Zahnlücke des Stirnrads der 2A in vergrößerter Darstellung, wobei eine Berührlinie eingezeichnet ist, die entsteht, wenn eine Schleifschnecke zum Schleifen des Stirnrads ohne Hubbewegung eingesetzt werden würde;
• 2C zeigt eine schematische Projektion einer Zahnlücke des Stirnrads der 2A in vergrößerter Darstellung, wobei mehrere Berührlinien eingezeichnet sind, die entstehen, wenn eine Schleifschnecke zum Schleifen des Stirnrads mit Hubbewegung eingesetzt wird;
• 3A zeigt eine schematische Seitenansicht einer beispielhaften Schleifschnecke, wobei anhand dieser Ansicht weitere Grundbegriffe definiert werden;
• 3B zeigt eine schematische Projektion einer Zahnlücke einer Schleifschnecke der 3A in vergrößerter Darstellung, wobei mehrere Berührlinien eingezeichnet sind, die entstehen, wenn die Schleifschnecke zum Schleifen eines Stirnrads eingesetzt wird;
• 3C zeigt eine stark schematisierte Abwicklung einer Zahnlücke der Schleifschnecke der 3A in vergrößerter Darstellung, wobei nur eine Berührlinie in schematischer Form angedeutet ist;
• 3D zeigt eine stark schematisierte Abwicklung einer einzelnen Schneckenflanke der Schleifschnecke der 3A in vergrößerter Darstellung, wobei mehrere Berührlinien in schematischer Form angedeutet sind.

Further details and advantages of the invention will be described below with reference to embodiments and with reference to the drawings.

• 1 shows a schematic perspective view of a grinding machine, which is designed to grind a workpiece with a grinding tool;
• 2A shows a schematic side view of an exemplary straight spur gear, based on this view basic concepts are defined;
• 2 B shows a schematic projection of a tooth gap of the spur gear of 2A in an enlarged view, wherein a Berührlinie is drawn, which arises when a grinding worm would be used for grinding the spur gear without lifting movement;
• 2C shows a schematic projection of a tooth gap of the spur gear of 2A in an enlarged view, wherein several Berührlinien are drawn, which arise when a grinding worm is used for grinding the spur gear with lifting movement;
• 3A shows a schematic side view of an exemplary grinding worm, based on this view further basic concepts are defined;
• 3B shows a schematic projection of a tooth gap of a grinding worm of 3A in an enlarged view, wherein a plurality of contact lines are drawn, which arise when the grinding worm is used for grinding a spur gear;
• 3C shows a highly schematic development of a tooth gap of the grinding worm of 3A in an enlarged view, wherein only one Berührlinie is indicated in a schematic form;
• 3D shows a highly schematic development of a single screw flank of the grinding worm of 3A in an enlarged view, with several Berührlinien are indicated in a schematic form.

DETAILED DESCRIPTION

In the context of the present description, terms are used which are also used in relevant publications and patents. It should be noted, however, that the use of these terms is for the convenience of understanding only. The inventive idea and the scope of the claims should not be limited by the specific choice of the terms in the interpretation. The invention can be readily applied to other conceptual systems and / or fields. In other fields the terms are to be applied mutatis mutandis.

2A shows a schematic side view of an exemplary straight-toothed spur gear W1 , whereby basic concepts are defined on the basis of this view. The spur gear W1 has a tooth width b2 and it is rotatable about the axis C arranged. Center in the representation of the 2A is a dental base ZG shown in gray. The rectangular area, which is here to the left of the tooth base ZG represents, represents a left tooth flank LF , The rectangular area, which is here to the right of the tooth base ZG represents a right tooth flank RF.

2 B shows a schematic projection of a single tooth gap 11 of the spur gear of 2A in an enlarged view. In this schematic projection, each tooth flank was projected separately and the tooth bottom ZG , which is shown here in gray, has been added schematically. In this particular form of projection is the tooth height h2 the teeth to the right and left of the tooth gap 11 significantly larger than the gap at the base of the tooth ZG , In addition, the tooth flanks LF . RF and the tooth base ZG represented in this projection as rectangular areas. The tooth heads are each to the right and left of the tooth flanks LF . RF arranged (not shown in 2 B ).

If you have the tooth gap 11 of the spur gear, for example, with a grinding wheel without lifting movement (ie without a relative movement axially parallel to the workpiece rotation axis C ), it would be a straight line as a line of contact BL , The touch line BL results from the moving points of contact, when the grinding wheel to the tool (rotation) axis B rotates. However, a straight line trace only results if there is no relative stroke movement parallel to the workpiece axis C ie, if the grinding wheel is not relative to the workpiece W1 emotional.

If a grinding worm 2 is used, then there is only a single Berührlinie BL , as in 2 B however, this contact line BL is shown in successive engagements of the grinding worm 2 is repeated several times.

The in 2 B Case shown is a special case, as for the gear grinding of the tooth flanks LF . RF along the entire tooth width b2 an axial feed parallel to the workpiece axis C is required. This axial feed is referred to here as a relative lifting movement and more generally also as a relative movement parallel to the workpiece rotation axis C.

2C shows a schematic projection of the same tooth gap 11 of the spur gear W1 of the 2A in an enlarged view, wherein a plurality of contact lines BL are drawn. These contact lines BL arise when a grinding worm 2 for grinding the spur gear W1 is used, which is a relative movement parallel to the workpiece axis C performs so as to the entire tooth width b2 to be able to handle grinding. Only five lines of contact BL are drawn in here so as not to overload the presentation. In practice, contact lines BL result along the entire tooth width b2 ,

Because a relative movement parallel to the workpiece axis C is specified, the contact point moves in a plane along the flank surfaces LF . RF but the touch lines BL run increasingly inclined with larger axial feed. At the presentation of 2C can be determined by the distance between two adjacent contact lines BL read the current axial feed Δx per workpiece revolution, as in 2C indicated.

The representations of the 2A to 2C referred to a straight toothed spur gear W1 , Now if you look at the situation at a grinding worm 2 considered, which is used as a grinding tool, one can there corresponding Berührlinien KBL define. These corresponding contact lines KBL However, they have a different shape. When defining the corresponding contact lines kBL, it is assumed here that a grinding worm 2 as a worm mathematically a helical gearing with a large helix angle (near 90 °) or small pitch angle (near 0 °) corresponds. In 3A is an exemplary grinding worm 2 shown in a side view. The grinding worm 2 has a width b0 and a diameter d0 , The tool (rotation) axis is provided with the reference symbol B.

In 3B is a projection of a tooth gap of the grinding worm 2 shown in an enlarged view. This projection is basically the projection of the 2 B and 2C However, the ratio of tooth width to tooth height is significantly greater. The picture of the 3B is not to scale. In this radial projection you can turn the two tooth flanks LF and RF , as well as the tooth base ZG detect. The tooth flanks LF and RF as well as the tooth heads (left and right next to the tooth flanks LF and RF ) are coated with abrasive grains, which are not visible here. The length of the tooth flanks LF and RF is called worm width b0 and the height of the tooth flanks LF and RF is called tooth height h0 designated.

At the presentation of 3B can be determined by the distance between two adjacent contact lines KBL the current axial feed Δz of the grinding worm 2 per revolution of the tool (ie per revolution of the grinding worm 2 ) read off. The axial feed Δz corresponds to the shift travel per tool revolution.

Due to the large helix angle or the small pitch, the projection shows the 3B only a strongly distorted image of the flank surfaces actually usable for grinding. Therefore, in 3C a development of the screw flanks shown in a schematic, highly simplified representation.

The development of the screw flanks is obtained by, for example, the center cylinder of the grinding worm 2 considered. This center cylinder cuts the flank surfaces of the flanks LF . RF in a helix (with a modified grinding worm 2 is generally only approximately a helix). The length of this helix is calculated as the quotient of the worm width b0 and the sine of the respective pitch angle of the tooth flank LF . RF on the center cylinder (diameter of the cylinder). As the diameter of the cylinder increases, the length of the helix increases. This means that the length of the helix is greatest at the head cylinder. The difference between the length of the helical line on the tooth head and the tooth root relative to the screw length is small, since the tooth height h0 relatively small with respect to the worm width b0 is.

Now, a reference diameter with a corresponding reference screw line and a reference screw length l0 * can be defined as follows: $$l0*=b0/\text{sin}\left(\gamma 0*\right)$$

γ0 * is the pitch angle at the reference diameter of the grinding worm 2 , From this conversion results the stretched representation of the 3C , whereby in principle the representation of the 3B was stretched by the factor 1 / sin (γ0 *). It should be noted that the contact line kBL, which in 3C shown is actually still much more would have to be stretched to meet the reality. It is also in 3C only a contact line kBL is shown, although the entire flanks LF, RF would have to be covered with such contact lines kBL.

In 3D is now the execution of a single screw flank (here the flank RF ) is shown in schematic form. There are shown here several contact lines kBL staggered to each other, which were chosen here for the sake of simplicity identical. Based on the distance between two adjacent contact lines KBL , you can in 3D read off the screw travel per tool revolution. This screw path corresponds to the Shiftweg .DELTA.s per tool revolution divided by the sine of the pitch angle γ0 *. At the touch lines KBL , in the 3D are shown, are rolling lines on a rectangle with the side lengths h0 (Tooth height) and l0 * (reference screw line length). The spacing of the contact lines kBL in this development thus corresponds to the screw travel per tool revolution about the tool (rotation) axis B. This screw path results from the shift path according to the above equation [1] .DELTA.s per tool revolution.

It can now be deduced that after a dressing operation, it is possible to achieve a better utilization of the abrasive grains by adjusting the ratio between the shifting and the axis-parallel movement. In at least part of the embodiments, therefore, this ratio is adjusted after a dressing operation or after several dressing operations. In other words, it comes with generating grinding with a grinding worm 2 with a large diameter d1 another relationship of the relative movement axially parallel or obliquely to the workpiece rotation axis C to the Shiftweg used than when grinding with a grinding worm 2 , their effective diameter d0 has become smaller by dressing.

In the following, the term "interference density EgD" is introduced. This engagement density EgD, which is considered along the helical lines or the tooth longitudinal direction, is defined as the reciprocal value for the screw travel per tool revolution. It is related to 3B the following equation: $$eGD={\left(\Delta z/\text{sin}\gamma \text{0 *}\right)}^{-1}$$

It is related to 3D the following equation: $$eGD=\Delta s·\text{sin}\gamma \text{0 *}$$

That is, the mesh density EgD defines the number of interventions per screw path. The mesh density EgD is at the maximum grinding wheel diameter d0max significantly lower than the minimum grinding worm diameter d0min (if the ratio of Shiftweg to paraxial movement is kept constant).

By defining the intervention density EGD , is now the first time a quantitative statement possible. Based on this quantitative statement, the grinding strategy can now be adapted to the grinding worm 2 better use. This in turn means that with a grinding worm 2 more workpieces W1 can be ground as before, by the application of the new grinding strategy (more precisely, it is a handling strategy), no deterioration of the surface quality of the ground tooth flanks is caused.

In the following, using a numerical example, the application of the mesh density EGD for setting a new handling strategy explained.

It is exemplified here by a constant stroke (ie with a constant axis-parallel relative movement parallel or obliquely to the workpiece rotation axis C ) with an axial feed of 0.3 mm / workpiece revolution (as in the prior art). It is also believed that the grinding worm 2 has a maximum diameter d0max = 350mm and a minimum diameter d0min = 220mm. Besides, the grinding worm has 2 a speed of 5 and the workpiece W1 is a spur gear with a number of teeth of 29.

The axial feed rate can be converted to the tool revolution as follows. The axial feed converted to the tool revolution corresponds to the stroke per tool revolution, ie: $$\frac{0.3mm\cdot 5}{29}=\mathrm{0,052}mm/WerkzeuGumdreHunG$$

The Shiftweg per tool revolution corresponds to the Shiftweg per engagement of a worm tooth of the grinding worm 2 , as follows: $$\frac{\mathrm{0,025}mm}{mm}\cdot \frac{\mathrm{0,052}mm}{WerkzeuGumdreHunG}=1.3\mu m/WerkzeuGumdreHunG$$

From this one can calculate the number of interventions per Shiftweg in the axial direction, and there are 769 interventions per mm worm width.

These sizes are all independent of the effective diameter d0 the grinding worm 2 , If, on the other hand, you take the (flank) area occupied by abrasive grains along the worm width b0 considered, the pitch angle plays a role. At the diameter d0max = 350mm, the pitch angle is only 2.05 °. At the diameter d0min = 220mm, however, the pitch angle is 3.26 °.

The screw travel per tool revolution corresponds to the path along the flank surface. With a grinding worm 2 with the diameter d0max , the screw travel per tool revolution is determined from Equation 2 as follows: $$\left(\frac{1.3\mu m}{WerkzeuGumdreHunG}\right)/\text{sin}\left(2.05°\right)=36.3\mu m/WerkzeuGumdreHunG$$

With a grinding worm 2 with the diameter d0min , the screw travel per tool revolution is determined from Equation 2 as follows: $$\left(\frac{1.3\mu m}{WerkzeuGumdreHunG}\right)/\text{sin}\left(3.26°\right)=\text{22}\text{, 9}\mu m/WerkzeuGumdreHunG$$

The screw travel per tool revolution is thus with a grinding worm 2 with a small diameter significantly smaller than with a grinding worm 2 with a large diameter. As a result of the dresser changing diameter thus changes the Schraubweg.

The number of interventions per screw path (this variable is referred to by definition as the mesh density EgD) is with a grinding worm 2 with the diameter d0max : EgD = 27.5 interventions per mm (along the flank surface). The number of interventions per screw path amounts to one grinding worm 2 with the diameter d0min : EgD = 43.7 interventions per mm (along the flank surface).

The mesh density EgD is at the maximum diameter d1max significantly lower than the minimum diameter d1min when the ratio of Shiftweg to paraxial movement is kept constant.

Now, in at least a part of the embodiments, a determination of a new grinding or handling strategy can be made based on the following approach. When the grinding worm 2 has been designed to work even when reaching the minimum diameter d0min still works reliably and delivers good grinding results, then starting from the mesh density EgD = 43.7 interventions per mm, a suitable adaptation of the grinding or handling strategy can be carried out as follows.

With reference to equation 2, a new screw travel per tool revolution can be determined backwards as follows: $$\frac{36.3\mu m}{22.9\mu m}=1.58\Rightarrow \frac{1.3\mu m}{1.58}=0.82\mu m,$$

That The screw travel per tool revolution can be reduced from 1.3μm to 0.82μm. A screw travel of 0.82 μm per tool revolution then corresponds to an engagement density per shift path (instead of an engagement density EgD per screw travel) of 1222 interventions per mm (along the worm width). From this a Shiftweg per stroke of 0.016mm / mm can be calculated (in general, this ratio is also referred to here as the ratio of Shiftwegs to the axis-parallel movement parallel or obliquely to the workpiece rotation axis C). This corresponds to a saving of 36% of the required shift travel for the considered stroke. This consideration is independent of the actual axial feed and thus applies to finishing and roughing strokes.

An example new grinding or handling strategy may now look like this, for example. Upon reaching the minimum diameter d0min For example, one shift travel per stroke of 0.025mm / mm can be specified. When grinding with a grinding worm 2 whose diameter is the maximum diameter d0max corresponds, for example, a Shiftweg per stroke of 0.016mm / mm can be specified. The grinding with a new (not yet or only little trained grinding worm 2 ) starts with a ratio of Shiftweg to stroke of 0.016. Assuming a linear relationship, then, after each dressing, the ratio of Shiftweg to stroke can be varied linearly from 0.016 to 0.025 stepwise.

This approach gives very good results, as more detailed studies have shown that the dependence of the mesh density EgD on the grinding wheel diameter d0 approximately linear.

If one continues to assume that when applying the conventional continuous shift strategy with a constant ratio of Shiftweg to the stroke 28 workpieces W1 each dressing could be machined with approx. 270 possible dressing processes, then with this conventional strategy it was possible to produce approx. 28 * 270 = 7560 workpieces W1 with a grinding worm 2 grind.

With the new shift or handling strategy, which provides for a variable ratio, it is possible to use approx. 43.5 workpieces at the maximum diameter instead of the 28 workpieces d0max finished before the first dressing. If one assumes a linear relationship, the number of over the entire diameter range of the grinding worm can 2 finished workpieces W1 estimate as follows: $$\left(\frac{43+28}{2}\right)\cdot 270=9652\text{workpieces}\text{,}$$

9652 workpieces are approx. 28% more than 7560 workpieces which can be ground with the conventional, continuous shift strategy. That is, by linearly adjusting the ratio of Shiftweg to stroke each after dressing, the grinding process can be significantly optimized.

The adaptation of the ratio of Shiftweg to the axis-parallel relative movement can also be dependent on the effective diameter d0 the grinding worm 2 be made. For this purpose, the diameter d0 are each determined after dressing, and then computationally using an equation, the ratio of Shiftweg for axis-parallel motion for the grinding operations, which follow after dressing, pretend.

Instead of the tooth height h0 For example, the scaled quantity h0 / cos (αn0) can also be used for the computational approximation to the tooth flank area, where αn0 is the normal intervention angle. Because the intervention density EGD in the above-described embodiments, for the sake of simplicity, in the direction of the helices (tooth longitudinal direction) was considered (see also 3D ), this was not necessary there.

A closer look at the distances between touchlines KBL can be done, for example, in which the distance Az not along the helix (as in 3D shown), but perpendicular to the contact lines KBL measured or calculated. For determining a corresponding engagement density along the perpendicular distance between the contact lines KBL , the just mentioned conversion must be made with the normal engagement angle αn0. Furthermore, however, the actual skew of the contact lines BL should be determined and taken into account.

From this approach, one obtains a somewhat more accurate equation that can be used in all embodiments after dressing to adjust the ratio of shift travel to axis-parallel motion.

Instead of making a linear adjustment of the ratio of Shiftweg axis-parallel relative movement, this adjustment can also be made non-linear in all embodiments after dressing.

Instead of making a linear adjustment of the ratio of Shiftweg to the axis-parallel relative movement, this adaptation can be done in all embodiments after dressing by reading previously stored values from a database (for example, by a table-look-up). In these embodiments, then a gradual (regional) adjustment of the ratio of Shiftweg for axis-parallel relative movement is used.

A grinding machine 100 The invention can eg with a tool spindle 1 for picking up and rotating a grinding tool 2 a tool rotation axis B (also referred to as tool axis) be equipped. Furthermore, the grinding machine 100 for example, a workpiece spindle 3 for picking up a workpiece W1 include. In addition, the machine includes 100 a dressing device 112 with a dresser 4 and the machine 100 is designed so that by means of the dresser 4 a dressing without reclamping the grinding tool 2 can be done. In 1 is in a snapshot dressing the grinding tool 2 with the dresser 4 shown.

Furthermore, the grinding machine includes 100 a controller 110 , In 1 is this control 110 indicated only by an oval, with the grinder 100 and / or with the dressing device 112 permanently or if necessary in communication connection stands. The communication connection is denoted by the reference numeral 111 Mistake.

In some of the embodiments, control takes over 110 the linear or non-linear adjustment of the ratio of Shiftweg to the stroke each time after dressing the grinding worm 2 ,

The arrangement and design of the axes of the grinding machine 100 are only an example. There are numerous other axle constellations that are also suitable. Also, the relative movements described herein do not have to be by moving a single axis (eg, the stroke axis X ). Each of the movements can also be generated by the superimposition of two or more than two axis movements.

The adaptation of said ratio is preferably carried out after each dressing of the grinding worm 2 , However, the adaptation of said ratio can also be carried out, for example, only after every second dressing or at a different interval.

Adjusting "after dressing" also includes adjusting that just before re-using a previously dressed grinding worm 2 can be done for Wälzschleifen.

The adaptation of said ratio can be done in small steps. If, for example, with a certain grinding worm 2 a total of 2000 workpieces W1 can be ground and if the mesh density EgD is between 0.01 and 0.03, then the difference between 0.03 and 0.01 can be divided by 2000. This gives 2000 micro-steps, each with 0,00001mm / mm. In this case, the controller takes 110 Step by step small changes in the ratio after each dressing before.

LIST OF REFERENCE NUMBERS

tool spindle 1 grinding tool 2 1. Workpiece spindle 3 trainer 4 gap 11 grinding machine 100 control 110 communication link 111 dressing 112 swivel axis A Normal pressure angle αn0 Workpiece axis C Tool (rotation) axis B contact line BL corresponding contact line KBL worm width b0 tooth width b2 diameter d0 maximum grinding worm diameter d0max minimum grinding worm diameter d0min Length along the winding / helix .DELTA.s Axial feed per workpiece revolution Ax Axial feed of the grinding worm per Az Tool rotation (screw revolution) intervention density EGD tooth height h0 Pitch angle at the reference diameter γ0 * left flank LF Referring screws (lines) length l0 * right flank RF (Gear) Workpiece W1 vertical axis X horizontal linear axis Y horizontal linear axis Z tooth root ZG

Claims (20)

A method of gear grinding a gear workpiece (W1) with a dressable grinding worm (2), wherein during grinding, the grinding worm (2) rotates about a tool rotation axis (B) and the gear workpiece (W1) rotates about a workpiece rotation axis (C) and relative movements are performed between the grinding worm (2) and the gear workpiece (W1), and after performing a dressing of the grinding worm (2) performed by a rotary drivable dresser (4), the following steps are performed: Performing a relative shift movement between the grinding worm (2) and the gear workpiece (W1) parallel to the tool rotation axis (B), - Performing an axially parallel relative movement between the grinding worm (2) and the gear workpiece (W1) parallel or obliquely to the workpiece rotation axis (C), wherein a ratio between the shift movement and the axis-parallel relative movement is predetermined, which is variable, so that during generating grinding a gear workpiece after the dressing process is used a different relationship than when Wälzschleifen a gear workpiece before the dressing process. Method according to Claim 1 , characterized in that reduced by each dressing process, the diameter (d0) of the grinding worm (2), and wherein the ratio between the shift movement and the axis-parallel relative movement changes. Method according to Claim 1 , characterized in that reduced by each dressing process, the diameter (d0) of the grinding worm (2), and wherein after each dressing, the ratio between the shift movement and the axis-parallel relative movement is increased. Method according to Claim 1 , characterized in that on the basis of an engagement density (EgD), which is tool-specific, the changing of the ratio between the shift movement and the axis-parallel relative movement is made. Method according to Claim 1 . 2 or 3 characterized in that the course of contact lines (kBL) on tooth flanks of the grinding worm (2) is determined in a preparatory method step, wherein the contact lines (kBL) during generating from contact between the gear workpiece (W1) and the grinding worm ( 2), and a mutual distance between at least two neighboring contact lines (kBL) is determined in order to calculate therefrom an engagement density (EgD) as the number of contact points per unit length. Method according to Claim 5 , characterized in that on the basis of this engagement density (EgD) a grinding strategy for the rolling grinding of a gear workpiece (W1) is defined, wherein the grinding strategy comprises a change in the ratio between the shift movement and the axis-parallel relative movement. Method according to Claim 5 , characterized in that based on this engagement density (EgD), the ratio between the shift and the axis-parallel relative movement (2) is defined. Method according to one of Claims 5 . 6 or 7 Characterized in that the change of the ratio between the shift movement and the axis-parallel relative movement is carried out so that the engagement density (EGD) when generating grinding of the gear workpiece (W1) remains constant or approximately constant, although by carrying out the dressing, the diameter (d0) reduces the grinding worm (2). Method according to one of Claims 5 . 6 or 7 , characterized in that the engagement density (EgD) is defined along helixes of the grinding worm (2) or along a tooth longitudinal direction of the grinding worm (2). Method according to one of Claims 5 to 8th , characterized in that the engagement density (EgD) is defined as the reciprocal of a screw travel per tool revolution. A grinding machine (100) comprising a spindle (1) for receiving and rotationally driving a grinding worm (2), a spindle (3) for receiving and rotationally driving a gear workpiece (W1), a dressing device (112) for receiving and rotationally driving a dresser (4) and having a plurality of NC controlled axes adapted to carry out relative movements between the grinding worm (2) and the gear workpiece (W1) and for dressing relative movements between the grinding worm (2) and the dresser (4), wherein the grinding machine (100) comprises a controller (110) which is connectable to the grinding machine (100) so that after dressing an axis-parallel relative movement between the grinding worm (2) and the gear workpiece (W1) and a relative shift movement between the grinding worm (2) and the gear workpiece (W1) are executable, wherein vorgebba a ratio between the shift movement and the axis-parallel relative movement r is variable, so that when Wälzschleifen a gear workpiece after dressing, a different relationship is used to when Wälzschleifen a gear workpiece before dressing. Grinding machine (100) after Claim 11 , characterized in that the grinding machine (100) and / or the controller (110) is adapted to allow in a preparatory method step to determine the course of contact lines (kBL) on tooth flanks of the grinding worm (2), wherein the contact lines ( kBL) result in a contact between the gear workpiece (W1) and the grinding worm (2) during rolling, and wherein a mutual distance between at least two adjacent contact lines (kBL) can be determined, in order to calculate an engagement density (EgD) as the number of contact points per unit length. Grinding machine (100) after Claim 11 or 12 , characterized in that the grinding machine (100) and / or the controller (110) is adapted to define a grinding strategy for the hobbing and dressing of a gear workpiece (W1) based on an engagement density (EgD), wherein the grinding strategy is a determination of the ratio. Grinding machine (100) after Claim 11 or 12 , characterized in that the grinding machine (100) and / or the controller (110) is designed to define based on an engagement density (EgD), the ratio between the shift movement and the axis-parallel relative movement. Grinding machine (100) according to one of Claims 11 . 12 or 13 , characterized in that the engagement density (EgD) along helical lines of the grinding worm (2) or along a tooth longitudinal direction of the grinding worm (2) is definable. Grinding machine (100) according to one of Claims 11 . 12 . 13 or 14 , characterized in that the engagement density (EgD) can be defined as a reciprocal value for a screw travel per tool revolution. Grinding machine (100) according to one of Claims 11 to 15 , characterized in that the engagement density (EgD) along helical lines of the grinding worm (2) or along a tooth longitudinal direction of the grinding worm (2) is definable. Grinding machine (100) according to one of Claims 11 to 16 , characterized in that the engagement density (EgD) can be defined as a reciprocal value to a screw travel per tool revolution. Grinding machine (100) after Claim 11 , characterized in that the grinding machine (100) comprises a computer, or an interface for connection to a computer, wherein the computer is designed to specify the relationship between the shift movement and the axis-parallel relative movement. Grinding machine (100) after Claim 11 , characterized in that the grinding machine (100) comprises a computer, or an interface for connection to a computer, the computer being designed to determine the course of contact lines (kBL) on tooth flanks of the grinding worm (2) in a preparatory method step. allow, wherein the contact lines (kBL) result in a Wälzschleifen from a contact between the gear workpiece (W1) and the grinding worm (2), and wherein a mutual distance between at least two adjacent contact lines (kBL) can be determined in order to allow the calculation of an engagement density (EgD) as the number of contact points per unit length.

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